The mechanical compensation method is generally used to change the focal length of a zoom lens, in which the zoom cam is a key component to achieve the continuous zoom of the zoom lens.In order to improve the quality of the zoom lens and reduce the size of component，the priciple of changing focal length of zoom lens by the mechanical compensation method is researched and the structure of zoom cam is analyzed with the software of NX/Nastran.Then,the optimization design of the zoom cam structure is achieved based on the analysis results.The final optimization results show that the mass of zoom cam has tightened by 88 g, the wall thickness reduced by 1.5mm, and the size of outside diameter decreased by 3 mm.The modal analysis and thermal analysis are carried out on the optimized zoom cam,it indicates that the cam’s first-order natural frequency is 50.3 Hz by modal analysis and the deformation size of cam in the temperature difference of 90 ℃ is 0.006 mm by thermal analysis.Finally, through the lens transfer function test,vibration test and high and low temperature tests, the correctness of finite element analysis and optimization analysis are proved,which indicates that the optimized design of zoom cam is successful.